The term "cotton" may be used in reference to either "seed cotton" or "lint." Seed cotton is the raw, natural flower of the cotton plant having the plant seed in intimate presence with the fiber of the flower. Lint is the flower fiber in isolation from the seed.
Cotton ginning includes drying and trash removal from the seed cotton, separation of the plant seed from the lint, additional trash removal from the lint, lint consolidation and bale packaging. Depending on the mechanical capacities of the process equipment, a cotton gin may process as much as 150,000 pounds of seed cotton per hour into 12,000 pounds per hour of lint that is packaged into 500 pound bales. As implied, a cotton ginning system consists of several different types of processing machines or devices. Each machine is designed to influence one or more physical properties of the lint product.
Lint quality after ginning is a function of its initial, natural quality as well as the type and degree of cleaning, drying or moisturizing it receives during the gin process. Fiber color, length, strength and density are natural attributes of quality. The presence of moisture and trash, however, are externally imposed quality characteristics susceptible to modification by mechanical influences. Research has established that the apparent strength of cotton fibers is directly proportional to fiber moisture content and is therefore greater at higher moisture levels. Consequently, as fiber moisture content is lowered, as by drying, the apparent strength is reduced and the frequency of fiber breakage during ginning is increased.
Being a hygroscopic material, the natural moisture content of cotton varies in relation to the relative humidity of the surrounding air. Cotton harvested during periods of high humidity may arrive at gins with a moisture content as high as 12 percent or more whereas cotton harvested during periods of low humidity may contain fiber moisture of 4 percent or less. For these reasons, gins seeking to gin lint at a predetermined moisture content must be prepared to add as well as remove moisture from the cotton being processed. Nevertheless, most cotton in the United States is processed in a standardized sequence without regard to actual quantities of trash or moisture present in an immediate process batch. Consequently, some cotton may be over dried or processed through more cleaners than necessary for the level of trash originally present in the cotton. Such unnecessary or even harmful processing can result in decreased fiber quality and increased cost and/or processing time.
Since much of the American cotton crop is harvested during low-humidity periods and often arrives at the gin with fiber moisture from 4 to 5 percent, the average fiber length of such cotton may be improved by adding moisture before fiber-seed separation and lint cleaning by reducing the number of fibers that break in the gin stands and lint cleaners. However, restoration of moisture to ginned lint will not improve fiber length. On the other hand, cotton with fiber moisture of 9 percent or more may neither gin smoothly nor process properly through the lint cleaners. Thus, the recommended fiber moisture level of 6.5 to 8 percent has a gin production aspect as well as a product quality aspect.
Removal of trash is primarily associated with the economics of market grade and price. However, there exists a point of diminishing returns where the benefits of further trash removal are offset by fiber and cottonseed damage and excessive loss of weight. Most modern gins contain cleaning equipment to handle the most severe trash condition that is expected in their service areas. Actual use of that equipment preferably should be based upon the incoming trash content of the cotton, and cleaner cottons should not be processed through every cleaning machine in the gin just because it is available. Trash removal should be restricted to that which is necessary to produce the grade determined by the color of the cotton. Further cleaning reduces the weight without increasing the value of the bale.
One way to optimize the cotton processing sequence is to control the temperature of equipment such as driers and to bypass certain machines, such as seed cotton cleaners and lint cleaners that may not be necessary for the particular cotton being processed. Traditionally, physical properties of the cotton such as trash content, moisture content, color, fiber length, length variation, fiber strength, fiber elongation and fiber thickness were not monitored as the gin process progressed. Consequently, no system or method existed to determine a process sequence that would optimize the lint product quality, grade or value. Since there was no method for determining the optimum quality sequence, there were no means or apparatuses for carrying out an optimum quality sequence.
Changing the number of cleaners used in a conventional cotton ginning system requires downtime for the system as well as labor costs for manually changing the valve configurations. It has been estimated that at least five minutes are required to change the valves on a single gin stand lint cleaner device, for those gin systems that are equipped with flow sequence change valves. A gin typically has three or more sets of lint cleaners in series or parallel processing lines but not all are equipped with bypass valves.
To bypass a machine such as a lint cleaner in a conventional ginning system, the flow of cotton is stopped through the gin stand that immediately precedes the lint cleaner. If equipped, the valves in the material flow conduits to the machine that is to be bypassed are then closed, usually manually. The bypassed machine is then stopped. To put the bypassed machine back online, the process must be reversed. In order to bypass a machine such as a seed cotton cleaner or drier, all of the preceding machines must be stopped which consequently stops the flow of cotton throughout the entire gin system for a period of several minutes while the seed cotton cleaner valves are manually changed.
More recently, the United States Department Of Agriculture and others have sponsored the development of online sensors for measuring color, moisture and trash values. Such developments are partially represented by U.S. Pat. No. 5,058,444 to W. S. Anthony et al, U.S. Pat. No. 5,087,120 to W. S. Anthony, and U.S. Pat. No. 5,639,955, also to W. S. Anthony. As relevant to the present invention, the entirety of these prior art patent disclosures are incorporated herein by reference.
U.S. Pat. No. 5,805,452, also incorporated entirely herein by reference, describes a cotton gin system having online sensors for the physical properties of color and moisture. Additionally, U.S. Pat. No. 5,805,452 teaches an online measurement of the relative trash content in the system flow stream. Data corresponding to these measurements is transmitted to a central processing unit (CPU). The CPU is a central control computer having a computer program logic that receives and processes the online sensor data to generate a gin decisional matrix from which flow sequence decisions are made that optimize the economic value of the flow stream. With a specific flow sequence concluded, appropriate operating signals are issued to powered flow controllers such as motor operated valves in the seed cotton or lint transport conduits.
Although U.S. Pat. No. 5,805,452 represents a significant stride toward online quality development, the variable data base contributed to the program logic still is only color, moisture and trash. Fiber length, fiber length variation, fiber strength, the elongation capacity of the fiber and the fiber perimeter and wall thickness related property of micronaire are not considered by the prior art program logic.
There is, therefore, need for an automatic gin control system that considers fiber strength, fiber length, fiber length variations, elongation capacity of the fiber and micronaire cotton properties along with color, moisture and trash in classing fiber samples.